Efficiency Question

[Morrey]

For three brews in a row after starting double grinding, I am seeing a trend that pre-boil efficiency is good, then brewhouse efficiency into fermenter jumps much higher. Just wanted to make sure I am looking at things correctly.

My process is propane fired BIAB, 5.5G batch size, full volume strike water, Arbor Fab mesh basket with press plate. Blichmann kettle sight glass used as a vol reference. Sight glass was tested with known volume for calibration reliability.

Schwarzbier Black Lager. 5# Pils, 4# Lt Munich, 6oz Blackprinz, 6oz C-60, 4 oz midnight wheat.

Mashed in and settled off at 150F (60 min) with 7.5G chemistry adjusted strike water, beginning ph rose slightly and tested 5.39 at the 30 minute mark while mid-mash stirring. Mashed out, raised basket (pulley) and pressed with press plate. Roughed up grain bed and rinse sparged with .35G distilled water and pressed again. Ended up with 7.35G pre-boil volume as .5G absorption is typical in my system. Using both a calibrated brix digital refractometer and a floating hydrometer as a secondary tester, SG reads 1.041 and was right at 85% pre-boil efficiency.

Did a 75 minute boil...extra 15 min basically to get rid of that extra water volume I sparged with. Used a Wilser hop sock (spider) and a paint strainer bag into fermenter. 5.75G into fermenter and the wort read 13.7 brix or 1.056 driving BH efficiency over 91%- a gain of 6% from pre-boil. HERE IS MY QUESTION: How is this possible to make such large gains in efficiency from pre-boil to Brew house?

I started double grinding with my motorized MM3 set pretty tight. When I started double grinding my efficiency numbers skyrocketed. I have no signs of astringency which may be a potential concern. Finished beers seem fine.

Thanks!

 

[McKnuckle]

It's impossible for efficiency to improve as the process progresses. It's all downhill from conversion, lauter, mash (pre-boil), to brewhouse. Or put another way; if you lose not a single drop of collected wort from pre-boil to the fermenter (not including evaporation), then your brewhouse efficiency will be equivalent to your mash efficency value.

 

[Biscuits]

What is your boil off rate set at in the software you use? I am wondering if the inputs you have are off. I am calculating your boil off at 1.28 G/hr...if you have it set at 1 G/hr it might be giving you incorrect target gravities.

 

[Morrey]

It's impossible for efficiency to improve as the process progresses. It's all downhill from conversion, lauter, mash (pre-boil), to brewhouse. Or put another way; if you lose not a single drop of collected wort from pre-boil to the fermenter (not including evaporation), then your brewhouse efficiency will be equivalent to your mash efficency value.

My question is based on this same (your) logic. How can BH eff be increasing from pre-boil. My numbers are there and very accurate. Where am I off in my calculations?

 

[Morrey]

What is your boil off rate set at in the software you use? I am wondering if the inputs you have are off. I am calculating your boil off at 1.28 G/hr...if you have it set at 1 G/hr it might be giving you incorrect target gravities.

I guess I have done this so many times I know the BO from experience so I don't adjust volume calculators anymore. 1.25G boil off per hour is my norm...of course ambient temps and humidity factor in, but 1.25GPH is my go to number and what I use in BeerSmith when I design recipes and set target gravities.

 

[doug293cz]

I agree with your mash efficiency (pre-boil efficiency) being 85%. I get 94% conversion efficiency and 89% lauter efficiency. I also get 90% brewhouse efficiency using your to fermenter numbers.

7.35 gal of wort at 1.041 (10.235 °P) gives the following weight of extract in the BK:

Extract = 7.35 gal * 8.3304 lb/gal * 1.041 * 0.10235 = 6.52 lb​

5.75 gal of wort at 13.7 °P (1.0556 SG) gives the following weight of extract in the BK:

Extract = 5.75 gal * 8.3304 lb/gal * 1.0556 * 0.137 = 6.93 lb​

Obviously it's not possible to gain 0.4 lb of extract going from the BK to the fermenter, so there must be one or more measurement errors somewhere.

For those who might be interested, I just posted a lengthy, very rigorous, tome on doing efficiency calculations here.

Brew on

 

[Morrey]

Obviously it is impossible to "gain" extract from the starting point meaning that brew house cant be higher than pre-boil unless I was adding in extract or sugars during the boil-which I am not. I have a measurement off somewhere so I am going to recalibrate my volumes. I may be off on my Ss BrewTech fermenter etch lines so I'll double check them for accuracy.

The link Doug provided to a previous thread was very helpful and made easy references to extract which makes the picture more clear. I believe my preboil volume to be accurate since I just checked the calibration scale on the sight glass recently. Pre-boil eff of 85% sounds about right, but the BH is skewed high probably due to a measuring error likely into fermenter.

These responses were helpful.

 

[pricelessbrewing]

Another likely source of measurement inaccuracy would be the preboil gravity. It's common for wort to not mix evenly very easily, meaning the wort from first runnings (mash drain off) and second runnings (from sparge) don't mix homogeneously, and the sample you pulled bring a poor representation of the preboil wort.

 

[Morrey]

Another likely source of measurement inaccuracy would be the preboil gravity. It's common for wort to not mix evenly very easily, meaning the wort from first runnings (mash drain off) and second runnings (from sparge) don't mix homogeneously, and the sample you pulled bring a poor representation of the preboil wort.

Good point! I am totally glad you brought this up since I realize now I probably didn't stir extremely well after sparging. Since I have been checking my volume calibrations carefully, I felt I had that nailed down. Darn, I bet my pre-boil reading was low...makes great sense now.

 

[McKnuckle]

Yep, that's a consistent bugaboo, the stirring. I measure pre-boil gravity when the boil is just about to start, and only after a very thorough mix. Even with the mixing, I still employ a small ladle and scoop a bit of wort from the bottom, top, and middle, and blend those into a measuring cup. I then take refractometer samples from the cup, at least two, as my pre-boil measurement.

 

[Morrey]

Yep, that's a consistent bugaboo, the stirring. I measure pre-boil gravity when the boil is just about to start, and only after a very thorough mix. Even with the mixing, I still employ a small ladle and scoop a bit of wort from the bottom, top, and middle, and blend those into a measuring cup. I then take refractometer samples from the cup, at least two, as my pre-boil measurement.

That's a good plan for sure. Like you and Doug said before (as I sat scratching my head) that the mash efficiency has to be the highest number, and the brew house can only be lower accounting for losses...not gains. Now I know where I went wrong and I'll remember your collection methods pre-boil. Always learning from each other. Thanks!!